Sensing of coil current is very important for operating and controlling SMPS circuits. Information about the current through the coil of the circuit is absolutely required that a control circuit can react accordingly to keep the coil current at level which provides correct output voltage Power consuming current sensing should be avoided, the current sensing circuits should be not complex and should not require significant area. Furthermore quiescent current should be reduced as far as any possible and noise immunity, which is especially important for switching mode power supplies, has to be minimized.